Explanatory Adequacy in Relational Quantum Mechanics: From Relational Events to Relational Histories

This paper examines the explanatory adequacy of formulations of relational quantum mechanics by distinguishing two levels of relationality. Intra-event relationality concerns the specification of a fact that obtains relative to a system in a particular interaction; inter-event relationality concerns the constraints connecting an event to subsequent events, physical records, and a relational history. Using established results from measurement theory, we show that an effect can specify the statistics of the current outcome without uniquely determining the conditional operation or the statistics of subsequent sequences. Likewise, a fixed coupling and ready state do not uniquely determine the structure of retrievable records unless the readout is specified. We accordingly introduce a task-relative criterion of explanatory adequacy: the required structures must be assessed against the particular explanatory role that a formulation assigns to an event, a relational fact, or a link between perspectives. The conclusion is not that RQM must derive instruments, dynamics, or linking rules from relational principles. A formulation that explicitly incorporates these structures can be fully adequate for the task in question. The paper contributes a distinction between intra-event and inter-event adequacy, a unified criterion for the division of explanatory labor, and a task-relative definition of an architectural deficit.